Audio Teleconferencing

Audio teleconferencing or audioconferencing is voice-only communication. Even though it lacks a visual dimension, audio teleconferencing has some major strengths: it uses the regular telephone system which is readily available and a familiar technology, it can connect a large number of locations for a conference, the conferences can be set up at short notice, and it is relatively inexpensive to use when compared with other technologies.
The interconnection medium for an audio teleconference is usually the telephone which can incorporate microwave, satellite, fiber optic or coaxial cable transmission. The conference call between three or more persons at different locations is the simplest type of audio teleconferencing. For multipoint teleconferencing among three or more sites an audio bridge is required to enable sites to interact clearly. The bridge links the telephone lines together so that parties at each location can hear and talk to each other. Olgren and Parker (1983) observe that there are many system options for audio teleconferencing, but the most common forms are:
  1. User-initiated conference calls or ("ad lib" teleconferencing);
  2. Operator-initiated or dial-up or (dial-out) teleconferencing;
  3. Dial-in or meet-me teleconferencing; and
  4. Dedicated audio networks.
In order to facilitate group-to-group communication, audio teleconferencing requires the use of some type of amplified telephone equipment with a loud speaker and microphones. The equipment may be built in to the room or may be portable. Audio teleconferencing equipment can be described as simplex, quasi-duplex or full-duplex depending on the kind of interactivity, and interruptibility of the conference connection.
Olgren and Parker (1983) observe that one should keep in mind that voice communication is the backbone of any teleconferencing system with the exception of computer conferencing. Sophisticated video or graphics equipment can be added to any audio system. But, it is the audio channel that is the primary mode of communication. If the audio is of poor quality it will have a negative impact on users of even the most sophisticated graphics and video technologies. This is very important to keep in mind because the evaluation of interactive television systems have shown (Dillon, Gunawardena, & Parker, 1992) that the most often cited technical problem in television systems is the poor audio quality. While expensive investments have been made in video and graphics systems, very little attention has been paid to the improvement of audio quality in video and audiographics conferencing systems.
Audio teleconferences can be enhanced by adding a visual component to the conference by mailing ahead of time printed graphics, transparencies or a video cassette to be used during the conference. Each site must be equipped with an overhead projector and a VCR if such graphical or video support is used.

Audiographics Conferencing

Audiographics systems use ordinary telephone lines for two-way voice communication and the transmission of graphics and written material. Audiographics add a visual element to audio teleconferencing while maintaining the flexibility and economy of using telephone lines. Audio teleconferencing is now combined with written, print, graphics and still or full motion video information. Most audiographics systems use two telephone lines, one for audio and one for the transmission of written, graphic and video information.
Currently, the simplest audiographics system is the addition of a fax machine using a second telephone line to an audio teleconference. Printed information can be exchanged during the conference using the fax machine so that visuals can be shared between sites. As a result of recent developments in computer, digital and video compression technology, fairly sophisticated computer-based audiographics systems are available in the market. These systems combine voice, data, graphics, and digitized still video to create a powerful communications medium. The PC-based systems have specially designed communications software that control a scanner; graphics tablet, pen, and key board; video camera, printer, and a modem.
One of the key advantages of an audiographics system is the ability to use the screen sharing feature of the system. Participants at different sites can use different colored pens to create a graphic on the same screen at the same time. This feature enables the use of collaborative learning methods that involve learners at the remote locations. Since each site is most often equipped with the same types of equipment, it is possible to originate instruction from any location. The systems allow for a higher degree of interaction than one-way video and two-way audio systems. If the system is equipped with a video camera, it is possible to bring video footage to the class or show three dimensional objects. High resolution full-color still video images can quickly be transmitted through dial up telephone lines. Some systems have incorporated a key pad device that is used for polling participant's opinions and feedback. When the instructor asks a multiple choice question, participants can use the keypad to key in their response. A central computer tabulates these responses and the instructor gets an instantaneous statistical summary of the entire group's responses, as well as how each site responded. This is a good way of soliciting and getting feedback from the participants , so that the instructor can adjust his or her presentation depending on the responses received.
Because audiographics systems use regular telephone lines, they are much more cost-effective than full motion video systems. Participants need to be present at locations equipped with the systems in order to participate in a conference and this may be inconvenient to some learners. The systems enable the transmission of audio, graphics, data and still video information and create a moderate sense of social presence. The human-interface depends to a large degree on the type of communications software that has been designed for the system. Most graphic systems can be mastered by novices with about one hour's training on the system.

Video Teleconferencing

Video teleconferencing systems transmit voice, graphics and images of people. They have the advantage of being able to show an image of the speaker, three dimensional objects, motion, and pre-produced video footage. The teleconference can be designed to take advantage of the three symbolic characteristics of the medium: iconic, digital and analog, where the iconic or the visual properties of the medium which is television's foremost strength can be manipulated to convey a very convincing message. Because of its ability to show the images of people, video teleconferences can create a "social presence" that closely approximates face-to-face interaction. Video teleconferencing systems are fully interactive systems that either allow for two-way video and audio, where the presenters and the audience can see and hear each other, or one-way video and two-way audio, where the audience sees and hears the presenter, and the presenter only hears the audience. During a video teleconference, audio, video and data signals are transmitted to distant sites using a single combined channel as in the use of a fiber optic line or on separate channels. Audio is most often transmitted over a dial-up telephone line. The transmission channel can be analog or digital; signals can be sent via satellite, microwave, fiber optics or coaxial cable or a combination of these delivery systems.
The term "video teleconferencing" has become popular as an "ad hoc" one time, special event conference that usually connects a vast number of sites in order to make the conference cost-effective. A video teleconference is usually distinguished from interactive Instructional Television (ITV) that is generally used to extend the campus classroom and carries programming for a significant length of time such as a semester. ITV may use the same transmission channels as a video teleconference, but is distinguished from video teleconferencing because of its different applications; video teleconferencing, an ad hoc conference, and ITV extending the classroom over a longer period of time.
Video teleconferences can be classified into two broad areas according to the technology used for transmission: full-motion video teleconferencing or compressed (or near-motion) video teleconferencing. Full-motion video teleconferencing uses the normal TV broadcast method or an analog video channel which requires a wideband channel to transmit pictures. The range of frequencies needed to reproduce a high quality motion TV signal is at least 4.2 million Hz (4.2 MHZ). The cost of a full-motion video teleconference is therefore extremely high. In the 1970s, conversion of the analog video signal to a digital bit stream enabled the first significant reductions in video signal bandwidth, making video conferencing less cost-prohibitive. Therefore, in compressed video, full video information is compressed by a piece of technology known as a Codec in order to send it down the narrower bandwidth of a special telephone line. The compressed video method is cheaper and more flexible than the TV broadcast method.
Full-motion video teleconferencing became popular with the advent of satellite technology. For the past decade educational developers have provided credit courses via satellite television over networks such as the National Technological University (for graduate engineering course), the Arts & Sciences Teleconferencing Service at Oklahoma State University, the TI-IN Network in Texas (for advanced placement high school courses).Both remote and urban schools and businesses have found these educational services valuable enough for their students and employees to make the investment in satellite hardware and tuition fees. Standard C- or Ku-band satellite TV signals can be received by consumer level hardware costing well under $2,000. For a producer of educational programming satellite delivery is still more economical than any other format for point-to-multipoint video transmission. Video compression standards and the introduction of fiber optic cable infrastructure by many telephone and cable companies promises to make terrestrial line transmission of video much cheaper in the near future.
There are, however, at least two reasons that satellite television will probably remain available and, in fact, increase in the foreseeable future. First, there are still many remote areas of the world, even in North America, where telephone service, if it exists at all, is supported by antiquated technology barely able to provide a usable audio or data signal, let alone carry video. These remote areas simply need to point a relatively inexpensive satellite dish, powered by solar panels, batteries, or generators, at the appropriate satellite to receive its signal. Additionally, new higher powered satellites are making it unnecessary to use today's large unwieldy satellite dishes. The new generation of Ku-band satellite is already offering direct broadcast service (DBS) to European households. These receivers known as VSAT's (or very small aperture terminals) are no larger than one to three feet in diameter and currently cost less than $500.
The proliferation of smaller, less expensive satellite television reception technology, along with the continued launching of new, higher powered satellites will insure a continuing niche for this technology to deliver instructional video and data to even the remotest areas of the world that lack other information infrastructure.
Fiber optics is gaining in popularity as a transmission medium for video teleconferencing. Fiber optics is a transmission technology using an attenuated glass fiber hardly thicker than a human hair, which conducts light from a laser source. A single glass fiber can carry the equivalent of 100 channels of television or 100,000 telephone calls, and even more capacity is possible by encasing many fibers within a cable. Fiber optics offers several advantages: it can carry a tremendous amount of data at high transmission speeds; it does not experience signal degradation over distance as does coaxial cable, and it is a multipurpose system which can transmit video, audio, data and graphics into the school through a single cable. A single fiber optic cable can carry over a billion bits per second, enabling several video teleconferences to run simultaneously. Many companies, universities and States in the United States are building fiberoptic transmission networks to carry voice, data and video.
Video teleconferencing can also use digital or analog microwave systems, or dial-up digital transmission lines. Current developments center on converging the different transmission channels and using a combination of telecommunications channels, satellite, fiber optic, microwave, coaxial cable to deliver full-motion video teleconferencing.

Compressed Video Teleconferencing

Video compression techniques have greatly reduced the amount of data needed to describe a video picture and have enabled the video signal to be transmitted at a lower, and less expensive data rate. The device used to digitize and compress an analog video signal is called a video codec, short for COder/DEcoder which is the opposite of a modem (MOdulator/DEModulator). Reduction of transmission rate means trade-offs in picture quality. As the transmission rate is reduced, less data can be sent to describe picture changes. Lower data rates yield less resolution and less ability to handle motion. Therefore, if an image moves quickly, the motion will "streak" or "jerk" on the screen.
Currently most compressed video systems use either T-1 or half a T-1 channel. In a T-1 channel, video is compressed at 1.536 Mbps which is the digital equivalent of 24 voice-grade lines. Many users of T-1 codecs opt for transmission at 768 kbps which is half a T-1 channel. The difference in video quality between transmission at 768 kbps and 1.536 Mbps is slight, but the savings in cost is significant. With the proliferation of fiber optic networks, some private video teleconferencing networks are taking advantage of high quality 45 Mbps transmission. Digital video compression technology has allowed video teleconferencing to become less cost-prohibitive. It is not as cost-effective as audio teleconferencing and audiographics teleconferencing, but may soon compete with more sophisticated audiographics systems with future developments in video compression technology.

Desk-top video teleconferencing

Future developments in video teleconferencing will move toward integrated desktop video teleconferencing combining audio, video and data. A fusion of network, personal computer, and digital video has produced the field of desktop videoconferencing. Saba (1993) observes that several telecommunications companies have introduced integrated systems (voice, video and data) that reside in a desktop computer and provide two-way synchronous communications with voice, image, file-transfer, and screen share capabilities. This technology allows users to see each other, speak to each other, transfer application files and work together on such files at a distance. Most systems do not require advanced digital communications technologies such as ISDN to operate. For those wanting to utilize ISDN, it is possible to purchase an ISDN card while most systems are now being designed to work with telecommunications standards such as ISDN.
Education can use this technology as a method of presenting class material and forming work groups even though they may be at a considerable distance from each other. An instructor could conceivably present material to the entire class either "live" or through delivery of an audio file to each students electronic mail account. Students could then work together in real time if they wished to share information over telephone lines.
In one current example, German officials are making use of desktop videoconferencing to form what has been dubbed a "Virtual Government". As planing progresses to move offices from Bonn, the current capital, to Berlin, planners meet regularly using online workstations rather than traveling to meetings. The results provide faster interaction at a much lower cost (Merwyn, 1993).
As more technologies begin to dovetail desktop videoconferencing becomes laptop videoconferencing. The use of cellular telephone technology combined with high speed laptop modems will make it possible for people to hold meetings and work group sessions whether they are at home, in an office or on the beach.

Interactive Instructional Television (ITV)

Interactive Instructional Television (ITV) systems usually use a combination of Instructional Television Fixed Service (ITFS) and point-to-point microwave. They can transmit either two-way video and two-way audio, or one-way video and two-way audio to several distant locations. The advantage of combining ITFS and microwave is that microwave is a point-to-point system while ITFS is a point-to- multipoint system. Therefore, large geographical areas can be covered by the combination of the two technologies. Microwave connects one location to another electronically with its point-to-point signals, while ITFS distributes that signal to several receiving stations around a 20 mile radius. In the U.S. several States such as Iowa and Oklahoma support statewide networks that use a combination of ITFS, microwave, satellite, fiber optics and coaxial cable.
In an ITFS and microwave television system, the course delivered over the system originates from a "studio classroom" on the campus. The classroom is specially designed to facilitate the extension of a conventional class through television. The audio feedback permits interaction between the teacher and students at distant locations. If a student viewing the class at a remote location has a question, he or she asks it through a talkback system, and it is heard by both on-campus and off-campus class members. The talk back system uses either the telephone, or FM microwave technology called radio talkback .
Interactive instructional television systems also use satellite, fiber optics, or compressed video to extend the traditional classroom. However, these systems are currently not as cost effective as systems that comprise of ITFS and point-to-point microwave.

Integrated Services Digital Network (ISDN)

ISDN is a new international telecommunications standard that offers a future worldwide network capable of transmitting voice, data, video, and graphics in digital form over standard telephone lines or fiber optic cable. ISDN transmits media using digital rather than analog signals. In order to move toward a global network, ISDN promises end-to-end digital connectivity, multiple services over the same transmission path and standard interfaces or conversion facilities for ubiquitous or transparent user access. Saba (1988) points out ISDN's applications for distance education: convergence, multitasking and shared communications. Convergence refers to the convergence on audio, video and data media in an integrated telecommunication system. Instruction is possible through voice, data, graphics, and video images. Multitasking refers to the variety of telecomputing capabilities that are available to the learner through integrated telecommunication systems that are based on minicomputers or microcomputers. Learners can gain access to online databases worldwide, and explore multimedia libraries comprising of digital sound, text and images. The shared communications feature allows the teacher and a group of learners separated by distance to work interactively on the same screen, sharing graphics, text, or data at the same time. Therefore, it is possible to solve a problem together or draw a graphic together even though a group of learners may be at different geographic locations. Currently available audiographics systems and desktop video teleconferencing systems provide for the features that will be available in a more user friendly and cost effective manner with the development of ISDN systems.

Broadcast Television and Radio.

Broadcast television and radio fall under the classification of Same Time/Different Place Instruction. The difference between broadcast television and radio and the previously discussed technologies under the same category is that broadcast television and radio do not provide for real time two-way interaction between presenters and participants. These media however can be used to instruct a vast number of students at the same time even though the students do not have the ability to call back and clarify a statement of ask a question in real time. Many distance education institutions in developing countries as well as institutions in developed countries such as the British Open University, use broadcast television and radio extensively to deliver programming to a large number of distant learners.
In the United States while television, both open-broadcast cable and ITV are the most popular media for delivering distance education, radio remains an underutilized medium (Gunawardena, 1988). It is in the developing countries that radio programming has been produced to either support and supplement print based materials or to carry the majority of the course content.
In the United States, the most common pattern of open-broadcast use for delivering distance education is for an institution to make arrangements with the Public Broadcasting Service (PBS) and/or a commercial television station to distribute the educational programming. One of the limitations of this type of distribution is that educational programming is confined to broadcast schedules predetermined by the broadcasting station, which may not be times convenient for students taking the course.
Bates (1984) observes that broadcasts are ephemeral, cannot be reviewed, are uninterruptable, and are presented at the same pace for all students. A student cannot reflect upon an idea or pursue a line of thought during a fast paced program, without losing the thread of the program itself. A student cannot go over the same material several times until it is understood.
Therefore, it is difficult for the learner to integrate or relate broadcast material to other learning. Hence, the need for broadcast programming to be accompanied by support materials in the form of pre-broadcast notes and follow-up exercises and activities. Research at the British Open University has indicated that "most students find it impossible to take notes while viewing, and those that do are usually very dissatisfied with their notes" (Bates, 1983 p.61). Access to a videotape of the broadcast, however, will alleviate these problems by giving the learner control over the medium with the ability to stop and rewind sections that were not clear.
Despite its ability to reach a large section of the student population, open-broadcast television is a one-way communication medium. It does not provide for interaction (two-way communication) between the student and the teacher and lacks flexibility and ability to respond to student feedback. Since students cannot question the instructor to clarify problems, and since professional broadcast production "makes the learner dependent on 'responsible' broadcasting" (Bates, 1983 p.61), this system of distribution can encourage passive acceptance of the instruction. To make the system interactive, open-broadcast distribution requires an added system to provide either an audio or audio-video return circuit.

Cable Television

In the United States, cable television began in remote rural areas, expanded into the suburbs, and has now penetrated into large urban areas. Cable has evolved from a way of improving reception in rural areas to a technology that is capable of providing many channels and even two-way video communication. Microwave relays have enabled cable operators to pick up signals from television stations too distant to be picked up over the air. Satellite interconnection of cable systems makes possible the importation of programming from virtually any part of the world. Today, cable technology is readily available and reaches a large number of homes and apartment units in the U.S.
Where cable can provide access to a large section of the population of a given geographic area, it can be used to distribute distance education. Cable can be used to replay programming offered over open-broadcast television, usually at more convenient times for the students than open-broadcast schedules, or used as a means of delivering nationally distributed television programs, where terrestrial broadcasting facilities are not available.
Interactive cable in most cases is not two-way video but one-way video with telephone feedback from the viewer to the instructor, or a technology that provides viewers with one-way video and one-way audio feedback combined with keypads or polling devices with which they can transmit impulses to a central computer in response to questions posed by the instructor. Student responses, such as "yes," "no," "do not understand," "slow down," etc., are immediately summarized by a central computer for the instructor, and often for the viewing audience, thereby adding an element of interaction to the experience.

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